Investigation on microstructure, wear and friction properties of CoCrFeNiMox high-entropy alloy coatings deposited by powder plasma arc cladding

Powder plasma arc cladding (PPA-C) is a promising method for crafting high-entropy alloy (HEA) coatings, providing significant advantages in terms of cost-effectiveness, superior quality, and exceptional efficiency. In this study, CoCrFeNiMox (x=0,0.5,1.0 and 1.5) HEA coatings were successfully prepared on 316 substrates using PPA-C technique. The influence of varying Mo concentrations on the microstructure, wear and friction properties of the alloy coatings were investigated. The results demonstrate that the introduction of Mo induces a transition in the alloy microstructure, shifting from a singular FCC phase (x=0) to a dual-phase FCC+σ (x=0.5, 1.0, and 1.5). With increasing content of Mo, solid solution strengthening, second phase strengthening and strengthening due to grain refinement occurred in the coatings, which lead to a notable increase in microhardness from 134.8 HV to 646.4 HV. Simultaneously, there was a notable enhancement in the wear resistance of the coatings (from 2.43×10-5 mm3/N·m to 3.47×10-6 mm3/N·m), accompanied by a decrease in the friction coefficient. This investigation introduces a cost-effective method for preparing HEA coatings, which can offer a systematic understanding of the friction properties in HEA coatings with varying Mo contents.